Deep 1.4 GHz Very Large Array Observations of the Radio Halo and Relic in Abell 2256

Enßlin, T. A.

doi:10.1086/504076

Cited by 145 publications

(217 citation statements)

References 70 publications

(101 reference statements)

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“…They reveal many new details in the relic and show that the relic has a significant amount of filamentary structure on scales down to ∼30kpc. Small-scale filamentary structures have also been seen for other relics, such as the Toothbrush cluster (van Weeren et al , 2016a, A3667 (Röttgering et al 1997), A3376 (Bagchi et al 2006), and in particular for Abell2256 (Clarke & Enßlin 2006;van Weeren et al 2009a;Owen et al 2014).…”

Section: Continuum Imagesmentioning

confidence: 84%

“…Radio relics often display spectral index gradients, with the spectral index steepening in the direction of the cluster center (e.g., Clarke & Enßlin 2006;Giacintucci et al 2008;van Weeren et al 2010;Bonafede et al 2012;Kale et al 2012;Stroe et al 2013). This spectral steepening is explained by synchrotron and Inverse Compton (IC) losses in the post-shock region of an outward traveling shock front.…”

Section: Spectral Index Mapsmentioning

confidence: 99%

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Chandra and JVLA Observations of HST Frontier Fields Cluster MACS J0717.5+3745

Weeren

Ogrean

Jones

et al. 2017

ApJ

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To investigate the relationship between thermal and non-thermal components in merger galaxy clusters, we present deep JVLA and Chandraobservations of the HST Frontier Fields cluster MACSJ0717.5+3745. The Chandraimage shows a complex merger event, with at least four components belonging to different merging subclusters. Northwestof the cluster, ∼0.7 Mpc from the center, there is a ram-pressure-stripped core that appears to have traversed the densest parts of the cluster after entering the intracluster medium (ICM) from the direction of a galaxy filament to the southeast. We detect a density discontinuity north-northeastof this core, which we speculate is associated with a cold front. Our radio images reveal new details for the complex radio relic and radio halo in this cluster. In addition, we discover several new filamentary radio sources with sizes of 100-300kpc. A few of these seem to be connected to the main radio relic, while others are either embedded within the radio halo or projected onto it. A narrow-angled-tailed (NAT) radio galaxy, a cluster member, is located at the center of the radio relic. The steep spectrum tails of this active galactic nucleuslead into the large radio relic where the radio spectrum flattens again. This morphological connection between the NAT radio galaxy and relic provides evidence for reacceleration (revival) of fossil electrons. The presence of hot 20 keV ICM gas detected by Chandranear the relic location provides additional support for this re-acceleration scenario.

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Section: Continuum Imagesmentioning

confidence: 84%

Section: Spectral Index Mapsmentioning

confidence: 99%

Chandra and JVLA Observations of HST Frontier Fields Cluster MACS J0717.5+3745

Weeren

Ogrean

Jones

et al. 2017

ApJ

Self Cite

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“…′ 9 × 7. ′ 8 (1125 kpc × 520 kpc) (Clarke & Ensslin 2006). Previous observations revealed that the radio relic includes filamentary structures (Clarke & Ensslin 2006;Brentjens 2008;Owen et al 2014).…”

Section: Cluster Of Galaxies Abell 2256mentioning

confidence: 97%

“…Radio observations have discovered a radio relic and a halo in the central part of Abell 2256 (Bridle & Fomalont 1976;Bridle et al 1979;Rottgering et al 1994;Miller et al 2003;Clarke & Ensslin 2006;Brentjens 2008;van Weeren et al 2009;Kale & Dwarakanath 2010;van Weeren et al 2012;Owen et al 2014;Trasatti et al 2015). The radio relic located in the north-west of the cluster is ∼ 440 kpc away from the X-ray center.…”

Section: Cluster Of Galaxies Abell 2256mentioning

confidence: 98%

JVLA S- and X-band polarimetry of the merging cluster Abell 2256

Ozawa

Nakanishi

Akahori

et al. 2015

Publications of the Astronomical Society of Japan

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We report polarimetry results of a merging cluster of galaxies Abell 2256 with Karl G. Jansky Very Large Array (JVLA). We performed new observations with JVLA at S-band (2051-3947 MHz) and X-band (8051-9947 MHz) in the C array configuration, and detected significant polarized emissions from the radio relic, Source A, and Source B in this cluster. We calculated the total magnetic field strengths toward the radio relic using revised equipartition formula, which is 1.8-5.0 µG. With dispersions of Faraday rotation measure, magnetic-field strengths toward Sources A and B are estimated to be 0.63-1.26 µG and 0.11-0.21 µG, respectively. An extremely high degree of linear polarization, as high as ∼ 35 %, about a half of the maximum polarization, was detected toward the radio relic, which indicates highly ordered magnetic lines of force over the beam sizes (∼ 52 kpc).The fractional polarization of the radio relic decreases from ∼ 35 % to ∼ 20 % around 3 GHz as the frequency decreases and is nearly constant between 1.37 and 3 GHz. Both analyses with depolarization models and Faraday tomography suggest multiple depolarization components toward the radio relic and imply the existence of turbulent magnetic fields.

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“…In some models, cluster shocks are even capable of providing enough energy to explain the entirety of the ARCADE-2 signal through the reacceleration of thermal electrons. Additionally, cluster shocks provide the larger magnetic fields necessary in order to efficiently convert electron energy into synchrotron radiation [57][58][59]. However, these models depend sensitively on the properties of cluster shocks in both major and minor mergers.…”

Section: Enhancement From Alfvén Reaccelerationmentioning

confidence: 99%

Anisotropy of the extragalactic radio background from dark matter annihilation

Fang

Linden

2015

Phys. Rev. D

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Observations of the extragalactic radio background have uncovered a significant isotropic emission across multiple frequencies spanning from 22 MHz to 10 GHz. The intensity of this non-thermal emission component significantly exceeds the expected contribution from known astrophysical sources. Interestingly, models have indicated that the annihilation of dark matter particles may reproduce both the flux and spectrum of the excess. However, the lack of a measurable anisotropy in the residual emission remains challenging for both dark matter and standard astrophysical interpretations of the ARCADE-2 data. We calculate the expected synchrotron anisotropy from dark matter annihilation and show that these models can produce very small anisotropies, though this requires galaxy clusters to have large substructure contributions and strong magnetic fields. We show that this constraint can be significantly relaxed, however, in scenarios where electrons produced via dark matter annihilation can be efficiently reaccelerated by Alfvén waves in the intra-Cluster medium. Our analysis indicates that any source capable of explaining the intensity and isotropy of the extragalactic radio excess must have a spatial extension far larger than typical for baryons in galaxies, hinting at a novel physics interpretation.

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Deep 1.4 GHz Very Large Array Observations of the Radio Halo and Relic in Abell 2256

Cited by 145 publications

References 70 publications

Chandra and JVLA Observations of HST Frontier Fields Cluster MACS J0717.5+3745

Chandra and JVLA Observations of HST Frontier Fields Cluster MACS J0717.5+3745

JVLA S- and X-band polarimetry of the merging cluster Abell 2256

Anisotropy of the extragalactic radio background from dark matter annihilation

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